Application of Filtration to Recover Solubilized Proteins During pH-Shift Processing of Blue Whiting (Micromesistius poutassou); Effects on Protein Yield and Qualities of Protein Isolates

Helgi Nolsoe*, a, Sofia K. Marmonb, Ingrid Undelandb
a Faroe Marine Research Institute, Nóatún 1, FO-110 Tórshavn, Faroe Islands
b Chalmers University of Technology, Chemical and Biological Engineering-Food Science, SE 41296 Göteborg, Sweden

© 2011 Nolsøe et al;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Faroe Marine Research Institute, Nóatún 1, FO-110 Tórshavn, Faroe Islands; Tel: +298353949; Fax: +298353901; E-mail:


Previous studies of the pH-shift protein isolation process have shown that substantial amounts of solubilized proteins can be trapped in the sediments formed in the first centrifugation step of this process. As a strategy to improve the protein yield during pH-shift processing, the aim of this study was to evaluate how filtration as an alternative to centrifugation in the first separation step of pH-shift processing of blue whiting affected proteins yield and protein isolate characteristics (basic composition, polypeptide profiles, surimi gel quality and color attributes). The study comprised both the acid and alkaline versions of the method, and also fresh as well as frozen fish raw material. Results showed that the replacement of centrifugation with filtration substantially improved the protein yield by from about 38% to 62%, but also reduced the removal of lipid. There were no significant effects on gel quality. Protein isolates from fresh raw material were about 5 % whiter and frozen raw materials about 3% whiter with centrifugation as compared to filtration in the pHshift process. For surimi from fresh raw material centrifugation gave about 2 % whiter gels, while the gels from frozen raw material were about 3% whiter for filtered compared to centrifuged material. The whitest isolates and gels were obtained with acid processing of fresh blue whiting. Slight proteolytic breakdown resulting in fragments of 83 and 152 kDa was however noted with the acid process, especially when centrifugation was used.

Keywords: Protein isolate, surimi, blue whiting, yield, gel strength, filtration, centrifugation..